Lithium-6 in HD 82943

This chart represents the spectrum of HD 82943, showing the region around the Lithium absorption line. The general shape of this spectral line is caused by Lithium-7 atoms in the atmosphere of the star, while the presence of Lithium-6 causes a certain asymmetry. Model computations have been used to calculate the amount of the two Lithium isotopes; the two fully drawn curves correspond to 6 Li/ 7 Li = 0.12 (red) and no Lithium-6 (0.00; blue), respectively. The difference (O-C = Observed - Calculated) is shown below and demonstrates the very good fit for an isotopic ratio of 0.12 (red dots).

Technical information: this image shows the spectrum of the V = 6.5 mag star HD 82943, as obtained on June 7, 2000, with the UVES spectrograph at the 8.2-m VLT KUEYEN telescope. It is based on three exposures made with Image Slicer 3 in Director's Discretionary Time in Service Mode, and each lasting 120 sec. The spectral resolution is 110,000 and the final S/N-ratio is about 500.